Control system and process for application of energy to airway walls and other mediums

ABSTRACT

The present invention includes a system for delivering energy to an airway wall of a lung comprising an energy delivering apparatus and a PID controller having one or more variable gain factors which are rest after energy deliver has begun. The energy delivering apparatus may include a flexible elongated member and a distal expandable basket having at least one electrode for transferring energy to the airway wall and at least one temperature sensor for measuring temperature. The PID controller determines a new power set point base on an error between a preset temperature and the measured temperature. The algorithm can be P i+1 =P i +G(αe i +βe i−1 +γe i−2 ) where α, β and γ are preset values and α is from 1 to 2; β is from −1 to −2; and γ is from −0.5 to 0-5. In another variation, the controller is configured to shut down if various measured parameters are exceeded such as, for example, energy, impedance, temperature, temperature differences, activation time and combinations thereof. Methods for treating a target medium using a PID algorithm are also provided.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to International Application No.PCT/US 00/28745 filed Oct. 17, 2000 which is hereby incorporated byreference in its entirety.

FIELD OF THE INVENTION

[0002] This invention is related to systems for applying energy to lungairways and in particular, to a system and method for controlling theenergy delivered to the airways using a PID algorithm to minimize errorbetween a preset temperature and a measured temperature.

BACKGROUND

[0003] Various obstructive airway diseases have some reversiblecomponent. Examples include COPD and asthma. There are an estimated 10million Americans afflicted with Asthma. Asthma is a disease in whichbronchoconstriction, excessive mucus production, and inflammation andswelling of airways occur, causing widespread but variable airflowobstruction thereby making it difficult for the asthma sufferer tobreathe. Asthma is a chronic disorder, primarily characterized bypersistent airway inflammation. Asthma is further characterized by acuteepisodes of additional airway narrowing via contraction ofhyper-responsive airway smooth muscle.

[0004] Reversible aspects of obstructive pulmonary disease generallyinclude excessive mucus production in the bronchial tree. Usually, thereis a general increase in bulk (hypertrophy) of the large bronchi andchronic inflammatory changes in the small airways. Excessive amounts ofmucus are found in the airways and semisolid plugs of mucus may occludesome small bronchi. Also, the small airways are narrowed and showinflammatory changes. Reversible aspects include partial airwayocclusion by excess secretions and airway narrowing secondary to smoothmuscle contraction, bronchial wall edema and inflammation of theairways.

[0005] In asthma, chronic inflammatory processes in the airway play acentral role in increasing the resistance to airflow within the lungs.Many cells and cellular elements are involved in the inflammatoryprocess, particularly mast cells, eosinophils T lymphocytes,neutrophils, epithelial cells, and even airway smooth muscle itself. Thereactions of these cells result in an associated increase in theexisting sensitivity and hyper-responsiveness of the airway smoothmuscle cells that line the airways to the particular stimuli involved.

[0006] The chronic nature of asthma can also lead to remodeling of theairway wall (i.e., structural changes such as thickening or edema) whichcan further affect the function of the airway wall and influence airwayhyper-responsiveness. Other physiologic changes associated with asthmainclude excess mucus production, and if the asthma is severe, mucusplugging, as well as ongoing epithelial denudation and repair.Epithelial denudation exposes the underlying tissue to substances thatwould not normally come in contact with them, further reinforcing thecycle of cellular damage and inflammatory response.

[0007] In susceptible individuals, asthma symptoms include recurrentepisodes of shortness of breath (dyspnea), wheezing, chest tightness,and cough. Currently, asthma is managed by a combination of stimulusavoidance and pharmacology.

[0008] Stimulus avoidance is accomplished via systematic identificationand minimization of contact with each type of stimuli. It may, however,be impractical and not always helpful to avoid all potential stimuli.

[0009] Pharmacological management of asthma includes: (1) long termcontrol through use of anti-inflammatories and long-actingbronchodilators and (2) short term management of acute exacerbationsthrough use of short-acting bronchodilators. Both of these approachesrequire repeated and regular use of the prescribed drugs. High doses ofcorticosteroid anti-inflammatory drugs can have serious side effectsthat require careful management. In addition, some patients areresistant to steroid treatment. The difficulty involved in patientcompliance with pharmacologic management and the difficulty of avoidingstimulus that triggers asthma are common barriers to successful asthmamanagement. Current management techniques are thus neither completelysuccessful nor free from side effects. Accordingly, it would bedesirable to provide a system and method which improves airflow withoutthe need for patient compliance.

[0010] Various energy delivering systems have been developed tointraluminally treat anatomical structures and lumen other than the lungairways. Unfortunately, the systems which are useful in treating suchstructures are generally not helpful in developing techniques to treatthe lung airways because the lung airways are markedly different thanother tissue structures. For example, lung airways are particularlyheterogeneous. Variations in lung tissue structure occur for a number ofreasons such as: the branching pattern of the tracheobronchial treeleads to local variation in the size and presence of airways; thevasculature of the lungs is a similar distributed network causingvariation in size and presence of blood vessels; within the airways arevariable amounts of differing structures such as cartilage, airwaysmooth muscle, and mucus glands and ducts; and energy delivery may alsobe influenced differently at the periphery, near the outer surface of alung lobe, than in the central portion.

[0011] Lung airways also include a number of protruding folds. Othertissue structures such as blood vessels typically do not have the foldsfound in airways. Airways contain mucous and air whereas otherstructures contain different substances. The tissue chemistry betweenvarious lumens and airways is also different. In view of thesedifferences, it is not surprising that conventional energy deliveringsystems cannot be universally applied to treat all tissue structures.Moreover, power shut-offs and other safety mechanisms must be preciselytailored to specific tissue so that the tissue is not harmed byapplication of excess energy.

[0012] Accordingly, an intraluminal RF energy delivering system that iscapable of safely delivering RF energy to lung airways is desired. Inparticular, a system which is capable of controlling the temperaturewhen treating an airway of an asthma or COPD patient is desired. It isalso desirable to provide a system having built-in safeguards that shutthe power off thereby preventing damage to the subject tissue orcollateral tissue.

SUMMARY OF THE INVENTION

[0013] The present invention includes a system for delivering energy toan airway wall of a lung comprising an energy delivering apparatus and aPID controller. The energy delivering apparatus may include a flexibleelongated member and a distal expandable basket having at least oneelectrode for transferring energy to the airway wall and at least onetemperature sensor for measuring temperature (T_(M)) of the airway wallwhen energy is delivered to the airway wall. The system furthercomprises a PID controller for determining a new power set point(P_(i+1)) based on an error (e) between a preset temperature (T_(S)) andthe measured temperature wherein the PID controller applies an algorithmhaving a variable gain factor (G).

[0014] In one variation of the present invention, the algorithm isP_(i+1)=P_(i)+G(αe_(i)+βe_(i−1)+γe_(i−2)) where α, β and γ are presetvalues. For instance, in one variation of the present invention, a isfrom 1 to 2; β is from −1 to −2; and γ is from −0.5 to 0.5. In anothervariation of the present invention, α, β, γ are 1.6, −1.6, and 0.0respectively.

[0015] In another variation of the present invention, the gain factorused in the PID algorithm is reset 0.1 to 2 seconds after energydelivery has begun. The gain factor can also be reset 0.5 seconds afterenergy delivery has begun. The invention includes resetting G to 0.9 to1.0 if a temperature rise in ° C. per Joule is less than or equal to2.5; 0.4 to 0.5 if a temperature rise in ° C. per Joule is between 2.5to 5.0; to 0.2 to 0.3 if a temperature rise in ° C. per Joule is equalto 5.0 to 7.5; and to 0.1 to 0.2 if a temperature rise in ° C. per Jouleis greater than 7.5. Initially, the gain factor is equal to 0.4 to 0.5and preferably 0.45 to 0.47.

[0016] In another variation of the present invention, the PID algorithmis P_(i+1)=P_(i)+(G₁e_(i)+G₂e_(i−1)+G₃e_(i−2)) and G₁, G₂ and G₃ arevariable gain factors. The invention includes configuring the controllersuch that G₁, G₂ and G₃ are reset to 0.9 to 2.00, −0.9 to −2.00 and 0.5to −0.5 respectively if a temperature rise in ° C. per Joule is lessthan or equal to 2.5; to 0.40 to 1.00, −0.40 to −1.00 and 0.25 to −0.25respectively if a temperature rise in ° C. per Joule is between 2.5 to5.0; to 0.20 to 0.60, −0.20 to −0.60 and 0.15 to −0.15 respectively if atemperature rise in ° C. per Joule is equal to 5.0 to 7.5; and to 0.10to 0.40, −0.10 to −0.40 and 0.10 to −0.10 respectively if a temperaturerise in ° C. per Joule is greater than 7.5. Each of the variable gainfactors may be equal to a product of at least one preset value and atleast one variable value.

[0017] In another variation of the present invention, the controller isconfigured such that the energy delivery is terminated if the energydelivered exceeds a maximum energy such as 120 joules.

[0018] In another variation of the present invention, the controller isconfigured to deliver energy for an activation time period such as up to15 seconds, 8 to 12 seconds, or 10 seconds.

[0019] In another variation of the present invention, the controller isconfigured such that T_(S) is set at a value between 60 to 80° C., or65° C.

[0020] In another variation of the present invention, the controller isconfigured to measure impedance and said energy delivery is terminatedwhen said impedance drops below a preset impedance value such as 40 to60 ohms.

[0021] In another variation of the present invention, the controller isconfigured to terminate the energy delivery if T_(M) exceeds T_(S) by apre-selected value such as 10, 15 or 20° C.

[0022] In another variation of the present invention, the controller isconfigured to terminate the energy delivery if the output power isgreater or equal to a nominal output power and T_(M) drops by a criticaltemperature difference within a sampling period. The invention includesa nominal output power set at a value of at least 17 watts; the samplingperiod is set at a value of at least 0.5 seconds; and the criticaltemperature difference is 2° C.

[0023] In another variation of the present invention, the controller isconfigured to terminate the energy delivery if said T_(M) averaged overa time window exceeds T_(S) by a fixed temperature difference. The fixedtemperature difference may be a value between 1 and 10° C. or 5° C. Thetime window is between 1 and 5 seconds or 2 seconds.

[0024] In another variation of the present invention, the controller isconfigured to terminate if the measured temperature drops by 10 or more° C. in a sample period such as 1.0 seconds or 0.2 seconds.

[0025] Another variation of the present invention is a method fortreating a lung by transferring energy from an active region of anenergy delivery apparatus to an airway wall of the lung. The energydelivery apparatus includes a flexible elongate body and a distalsection and the active region is located in the distal section. Theenergy delivery apparatus further has a temperature sensor located inthe distal section for measuring a temperature (T_(M)) of said airwaywall and the method comprises the following steps: setting a presettemperature (T_(S)); determining a power set point (P_(i)) to deliverenergy from the active region to the target medium; measuring the T_(M)using the temperature sensor; and determining a new power set point(P_(i+1)) based on an error (e) between the preset temperature (T_(S))and the measured temperature (T_(M)) using a PID algorithm.

[0026] In yet another variation of the present invention, a process fortransferring energy to a target medium using an energy deliveryapparatus is provided. The energy delivery apparatus includes a flexibleelongate body and a distal section wherein the distal section includesan expandable basket with at least one active region for transferringenergy to the target medium. The energy delivery apparatus further has atemperature sensor located in the distal section for measuring atemperature (T_(M)) of the target medium. The process comprises thefollowing steps: setting a preset temperature (T_(S)); determining apower set point (P_(i)) to deliver energy from the active region to thetarget medium; measuring T_(M) using the temperature sensor; anddetermining a new power set point (P_(i+1)) based on an error (e)between the preset temperature (T_(S)) and the measured temperature(T_(M)) using an algorithm having a variable gain factor. The energy maybe delivered to an airway wall of a lung in vivo, in vitro or to anothertarget such as a sponge or towel which may be moistened with salinesolution. Saline solution increases the conductivity of the target.

[0027] In one variation of the present invention, the algorithm isP_(i+1)=P_(i)+G(αe_(i)+βe_(i−1)+γe_(i−2)) where α, β and γ are presetvalues: a is from 1 to 2; β is from −1 to −2; and γ is from −0.5 to 0.5.In another variation of the present invention, α, β, γ are 1.6, −1.6,and 0.0 respectively.

[0028] In another variation of the present invention, the gain factor isreset 0.1 to 2 seconds after energy delivery has begun. The gain factorcan also be reset 0.5 seconds after energy delivery has begun. Theinvention includes resetting G to 0.9 to 1.0 if a temperature rise in °C. per Joule is less than or equal to 2.5; 0.4 to 0.5 if a temperaturerise in ° C. per Joule is between 2.5 to 5.0; to 0.2 to 0.3 if atemperature rise in ° C. per Joule is equal to 5.0 to 7.5; and to 0.1 to0.2 if a temperature rise in ° C. per Joule is greater than 7.5.Initially, the gain factor is equal to 0.4 to 0.5 and preferably 0.45 to0.47.

[0029] In another variation of the present invention, the energydelivery is terminated if the energy delivered exceeds a maximum energysuch as 120 joules.

[0030] In another variation of the present invention, energy isdelivered for an activation time period such as 0 to 15 seconds, 8 to 12seconds, or 10 seconds.

[0031] In another variation of the present invention, T_(S) is set at avalue between 60 to 80, or 65° C.

[0032] In another variation of the present invention, impedance ismeasured and energy delivery is terminated when the impedance dropsbelow a preset impedance value such as 40 to 60 ohms.

[0033] In another variation of the present invention, the energy isterminated if T_(M) exceeds T_(S) by a pre-selected value such as 10, 15or 20° C.

[0034] In another variation of the present invention, energy isterminated if the output power is greater or equal to a nominal outputpower and T_(M) drops by a critical temperature difference within asampling period. In variations of the present invention, the nominaloutput power is set at a value of at least 17 watts; the sampling periodis set at a value of at least 0.5 seconds; and the critical temperaturedifference is 2° C.

[0035] In another variation, the energy delivery apparatus is configuredto deliver an amount of power up to a maximum power. The maximum powercan be from 10 to 40 watts and preferably from 15 to 20 watts.

[0036] In another variation of the present invention, energy delivery isterminated if T_(M) averaged over a time window exceeds T_(S) by a fixedtemperature difference. The fixed temperature difference may be a valuebetween 1 and 10° C. or 5° C. The time window is between 1 and 5 secondsor 2 seconds.

[0037] In another variation of the present invention, the energydelivery is terminated if the measured temperature drops by 10 or more °C. in a sample period such as 1.0 seconds or 0.2 seconds.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The invention will now be described in greater detail withreference to the various embodiments illustrated in the accompanyingdrawings:

[0039]FIG. 1 is a block diagram of a feedback loop of the presentinvention.

[0040]FIG. 2A is a cross sectional view of a medium sized bronchus in ahealthy patient.

[0041]FIG. 2B is a cross sectional view of a bronchiole in a healthypatient.

[0042]FIG. 3 is a cross sectional view of the bronchus of FIG. 2Ashowing the remodeling and constriction occurring in an asthma patient.

[0043]FIG. 4 is an illustration of the lungs being treated with a deviceand controller according to the present invention.

[0044]FIG. 5A is an illustration of an energy delivery device inaccordance with the present invention.

[0045] FIGS. 5B-5D show a partial view of a thermocouple attached to abasket leg in accordance with the present invention.

DETAILED DESCRIPTION

[0046] The present invention includes a controller and an energy deliverapparatus to deliver energy to the airway walls of the lungs. Amongstother features, the controller includes a feedback loop having avariable gain factor as diagramed in FIG. 1. The system is useful intreating asthma and various symptoms of reversible obstructive pulmonarydisease. Examples of suitable applications and methods are disclosed inInternational Application No. PCT/US00/28745 filed Oct. 17, 2000.

[0047] The present invention is particularly useful in treating lungtissue. This is surprising in view of the unique and complicatedstructure of lung tissue. Referring first to FIGS. 2A and 2B, a crosssection of two different airways in a healthy patient is shown. Theairway of FIG. 2A is a medium sized bronchus having an airway diameterD1 of about 3 mm. FIG. 2B shows a section through a bronchiole having anairway diameter D2 of about 1.5 mm. Each airway includes a folded innersurface or epithelium 10 surrounded by stroma 12 and smooth muscletissue 14. The larger airways including the bronchus shown in FIG. 2Aalso have mucous glands 16 and cartilage 18 surrounding the smoothmuscle tissue 14. Nerve fibers 20 and blood vessels 24 surround theairway. The airway is thus quite different from other tissues such asblood vessel tissue which does not include such folds, cartilage ormucous glands. In contrast, FIG. 3 illustrates the bronchus of FIG. 2Ain which the smooth muscle 14 has hypertrophied and increased inthickness causing the airway diameter to be reduced from the diameter D1to a diameter D3. Accordingly, the airways to be treated with the deviceof the present invention may be 1 mm in diameter or greater, morepreferably 3 mm in diameter or greater.

[0048]FIG. 4 is an illustration of the lungs being treated with a system36 according to the present invention. The system 36 includes acontroller 32 and an energy treatment device 30 which may be anelongated member as described further below. The device 30 also includesan expandable distal section which can be positioned at a treatment site34 within a lung or another target medium. In operation, the device ismanipulated to the treatment site 34. RF energy, for example, isdelivered through the energy delivering device and penetrates thesurface of the lung tissue such that tissue is affected below theepithelial layer as well as on the surface of the lung tissue.

[0049] Energy Delivering Device

[0050] As indicated above, the present invention includes a controller32 and a device 30 through which it delivers energy to the target medium34. A device 30 of the present invention should be of a size to accessthe bronchus or bronchioles of the human lung. The device may be sizedto fit within bronchoscopes, preferably, with bronchoscopes having aworking channel of 2 mm or less. The device may also include a steeringmember configured to guide the device to a desired target location. Forexample, this steering member may deflect a distal tip of the device ina desired direction to navigate to a desired bronchi or bronchiole.

[0051] The energy delivering apparatus 30 typically includes an elongatebody having a proximal section and a distal section. The distal sectionfeatures a radially expandable basket having a plurality of legs. Thelegs may be electrodes or have an active region defined by an insulatedcovering which contacts the medium to be treated. The basket is expandedwith an actuator mechanism which may be provided in a handle attached toproximal end of the elongate body. Examples of energy delivering devicesin accordance with the present invention are described in co-pendingU.S. application Ser. No. 09/436,455 filed Nov. 8, 1999 which is herebyincorporated by reference in its entirety.

[0052] Temperature Sensor

[0053] The invention also includes a temperature detecting element.Examples of temperature detecting elements include thermocouples,infrared sensors, thermistors, resistance temperature detectors (RTDs),or any other apparatus capable of detecting temperatures or changes intemperature. The temperature detecting element is preferably placed inproximity to the expandable member.

[0054]FIG. 5A is a partial view of a variation of the invention havingthermocouple 137 positioned about midway along basket leg 106. FIG. 5Bis an enlarged partial view of the thermocouple 137 of FIG. 5A showingthe leads 139 separately coupled on an inwardly-facing surface of theleg 106. Consequently, the basket leg itself is used as part of thethermocouple junction upon which the temperature measurement is based.In other words, the thermocouple junction is intrinsic to the basketleg. This configuration is preferred because it provides an accuratetemperature measurement of tissue contacting the leg 106 in the vicinityof the thermocouple leads. In contrast, typical thermocoupleconfigurations consist of a thermocouple junction offset or extrinsic tothe basket leg. We believe that thermocouple junctions having an offsetfrom or extrinsic to the basket leg do not measure temperature asaccurately in certain applications as thermocouple junctions which areintrinsic to the basket leg.

[0055] The leads 139 may be placed at other locations along the leg 106including an edge 405. Joining the leads 139 to the edge 405, however,is undesirable because of its relatively small bonding surface.

[0056]FIG. 5B also shows basket leg 106 having an outer insulatingmaterial or coating 410. The boundaries 415 of the insulating material410 define an uninsulated, active section of electrode leg 106 whichdelivers energy to the tissue walls. Preferably, the insulating coating410 is heat shrink tubing or a polymeric coating. However, otherinsulating materials may be used.

[0057]FIGS. 5C and 5D show another variation of the present inventionhaving thin foil or laminated thermocouple leads 139. The thermocoupleleads 139 are configured as foils or layers which can be, for example,prefabricated foils or sputtered films. Suitable materials for thethermocouple leads (listed in pairs) include, but are not limited to:Constantan and Copper; Constantan and Nickel-Chromium; Constantan andIron; and Nickel-Aluminum and Nickel-Chromium. The thermocouple pair,CHROMEL and ALUMEL (both of which are registered trademarks of HoskinsManufacturing) is preferred. CHROMEL and ALUMEL is a standardthermocouple pair and has been shown to be biocompatible and corrosionresistant in our applications. The thermocouple leads 139 may be placedsuch that each lead approaches the center of the basket leg from anopposite end of the basket leg. The leads 139 then terminate in bondjoints 440 and 450. Alternatively, as shown in the configuration of FIG.5D, both thermocouple leads 139 may run from the same end of the basketleg 106.

[0058] Preferably, insulating layers 430 and 440 are disposed betweenthe thin film leads 139 and the basket leg 106. The insulating layers430 and 440 electrically separate the leads 139 as well as electricallyseparate the leads from the leg 106. The insulating layers 430 and 440limit the thermocouple junction to bond joints 450 and 460, which areoptimally positioned on active region 420 of basket leg 106.

[0059] Controller

[0060] The present invention includes a controller which controls theenergy to be delivered to the airways via an energy transfer device. Thecontroller includes at least one of the novel features disclosedhereinafter and may also incorporate features in known RF energycontrollers. An example of a RF generator which may be modified inaccordance with the present invention is the FORCE™ 2 Generatormanufactured by Valleylab, Boulder, Colo., U.S.A. Another suitabletechnique to generate and control RF energy is to modulate RF output ofa RF power amplifier by feeding it a suitable control signal.

[0061] The controller and power supply is configured to deliver enoughenergy to produce a desired effect in the lung. The power supply shouldalso be configured to deliver the energy for a sufficient duration suchthat the effect persists. This is accomplished by a time setting whichmay be entered into the power supply memory by a user.

[0062] The power supply or generator of the present invention can alsoemploy a number of algorithms to adjust energy delivery, to compensatefor device failures (such as thermocouple detachment), to compensate forimproper use (such as poor contact of the electrodes), and to compensatefor tissue inhomogeneities which can affect energy delivery such as, forexample, subsurface vessels, adjacent airways, or variations inconnective tissue.

[0063] The power supply can also include circuitry for monitoringparameters of energy transfer: (for example, voltage, current, power,impedance, as well as temperature from the temperature sensing element),and use this information to control the amount of energy delivered. Inthe case of delivering RF energy, typical frequencies of the RF energyor RF power waveform are from 300 to 1750 kHz with 300 to 500 kHz or 450to 475 being preferred. The RF power-level generally ranges from about0-30 W but depends upon a number of factors such as, size of theelectrodes. The controller may also be configured to independently andselectively apply energy to one or more of the basket leg electrodes.

[0064] A power supply may also include control modes for deliveringenergy safely and effectively. Energy may be delivered in open loop(power held constant) mode for a specific time duration. Energy may alsobe delivered in temperature control mode, with output power varied tomaintain a certain temperature for a specific time duration. In the caseof RF energy delivery via RF electrodes, the power supply may alsooperate in impedance control mode.

[0065] Temperature Control Mode

[0066] In a temperature control mode, the power supply may operate up toa 75° C. setting. That is, the temperature measured by the thermocouplecan reach up to 75° C. before the power supply is shut off. The durationmust be long enough to produce the desired effect, but as short aspossible to allow treatment of all of the desired target airways withina lung. For example, up to 15 seconds is suitable, and more preferably 8to 12 seconds with about 10 seconds per activation (while the device isstationary) being preferred. Shorter duration with higher temperaturewill also produce an acceptable acute effect.

[0067] It should be noted that different device constructions utilizedifferent parameter settings to achieve the desired effect. For example,while direct RF electrodes typically utilize temperatures up to 75° C.in temperature control mode, resistively heated electrodes may utilizetemperatures up to 90° C.

[0068] Energy Pulses and Energy Modulation

[0069] Short bursts or pulses of RF energy may also be delivered to thetarget tissue. Short pulses of RF energy heat the proximal tissue whilethe deeper tissue, which is primarily heated by conduction through theproximal tissue, cools between the bursts of energy. Short pulses ofenergy therefore tend to isolate treatment to the proximal tissue.

[0070] The application of short pulses of RF energy may be accomplishedby modulating the RF power waveform with a modulation waveform.Modulating the RF power waveform may be performed while employing any ofthe other control algorithms discussed herein so long as they are notexclusive of one another. For example, the RF energy may be modulatedwhile in a temperature control mode.

[0071] Examples of modulation waveforms include but are not limited to apulse train of square waves, sinusoidal, or any other waveform types. Inthe case of square wave modulation, the modulated RF energy can becharacterized in terms of a pulse width (the time of an individual pulseof RF energy) and a duty cycle (the percent of time the RF output isapplied). A suitable duty cycle can be up to 100% which is essentiallyapplying RF energy without modulation. Duty cycles up to 80% or up to50% may also be suitable for limiting collateral damage or to localizethe affect of the applied energy.

[0072] Feedback Algorithm

[0073] As indicated above, the present invention includes controllershaving various algorithms. The algorithms may be either analog anddigital based. A preferred embodiment is a three parameter controller,or Proportional-Integral-Derivative (PID) controller which employs thefollowing algorithm: P_(i+1)=P_(i)+G(αe_(i)+βe_(i−1)+γe_(i−2)) whereP_(i+1) is a new power set point, P_(i) is a previous power set point,α, β and γ are preset values, G is a variable gain factor and e_(i),e_(i−1), e_(i−2) correspond to error at the present time step, error onestep previous and error two steps previous where the error is thedifference between the preset temperature and a measured temperature.

[0074] We have found that by using a variable gain factor (G) toadaptively control RF energy delivery, the system of the presentinvention can treat a wide range of tissue types including lung tissuebronchus, bronchioles and other airway passages. The variable gainfactor scales the coefficients (alpha, beta, and gamma; each a functionof the three PID parameters) based on, for example, the temperatureresponse to energy input during the initial temperature ramp up.

[0075] Exemplary PID parameters are presented herein, expressed inalpha-beta-gamma space, for an energy delivering device and controllerof the present invention. These settings and timings are based ontesting in various animal lung tissues using an energy deliveringapparatus as described above. First, the gain factor preferably variesand is reset 0.1 to 2 and more preferably at 0.5 seconds after energydelivery has begun. Preferably, the gain factor is reset as follows: Gis reset to 0.9 to 1.0 and preferably 0.9 if a temperature rise in ° C.per Joule is less than or equal to 2.5; G is reset to 0.4 to 0.5 andpreferably 0.5 if a temperature rise in ° C. per Joule is between 2.5 to5.0; G is reset to 0.2 to 0.3 and preferably 0.2 if a temperature risein ° C. per Joule is equal to 5.0 to 7.5; and G is reset to 0.1 to 0.2and preferably 0.1 if a temperature rise in ° C. per Joule is greaterthan 7.5. We have also found that a suitable value for α is from 1 to 2;for β is from −1 to −2; and for γ is from −0.5 to 0.5. More preferablyα, β, γ are 1.6, −1.6, and 0.0 respectively.

[0076] It is also possible to change the relative weights of alpha,beta, and gamma depending upon monitored temperature response working ineither PID or Alpha-Beta-Gamma coordinate space beyond just scaling thealpha-beta-gamma coefficients with a variable gain factor. This can bedone by individually adjusting any or all of alpha, beta, or gamma.

[0077] In another variation of the present invention, the PID algorithmis P_(i+1)=P_(i)+(G₁e_(i)+G₂e_(i−1)+G₃e_(i−2)) and G₁, G₂ and G₃ areeach variable gain factors. The invention includes configuring thecontroller such that G₁, G₂ and G₃ are reset to 0.90 to 2.00, −0.90 to−2.00 and 0.50 to −0.50 respectively if a temperature rise in ° C. perJoule is less than or equal to 2.5; to 0.40 to 1.00, −0.40 to −1.00 and0.25 to −0.25 respectively if a temperature rise in ° C. per Joule isbetween 2.5 to 5.0; to 0.20 to 0.60, −0.20 to −0.60 and 0.15 to −0.15respectively if a temperature rise in ° C. per Joule is equal to 5.0 to7.5; and to 0.10 to 0.40, −0.10 to −0.40 and 0.10 to −0.10 respectivelyif a temperature rise in ° C. per Joule is greater than 7.5. Each of thevariable gain factors may be equal to a product of at least one presetvalue and at least one variable value.

[0078] It is also possible to employ an algorithm that continuouslyadapts to signals rather than at discrete sample steps, intervals orperiods. The algorithm takes into account several variables upon whichobserved temperature response depends including, for example: initialtemperature, time history of energy delivery, and the amount of energyrequired to maintain set point temperature. An exemplary analog PIDalgorithm is: u=K_(P)e+K_(I)∫edt+K_(D)(de/dt) where u is a signal to beadjusted such as, for example, a current, a voltage difference, or anoutput power which results in energy delivery from the electrode to theairway wall. K_(P), K_(I) and K_(D) are preset or variable values whichare multiplied with the proper error term where e(t) is the differencebetween a preset variable and a measured process variable such astemperature at time (t). The above equation is suitable for continuousand/or analog type controllers.

[0079] Power Shut Down Safety Algorithms

[0080] In addition to the control modes specified above, the powersupply may include control algorithms to limit excessive thermal damageto the airway tissue. Damage may be limited by terminating or shuttingdown the energy being delivered to the target medium. The algorithms canbe based on the expectation that the sensed temperature of the tissuewill respond upon the application of energy. The temperature response,for example, may be a change in temperature in a specified time or therate of change of temperature. The expected temperature response can bepredicted as a function of the initially sensed temperature, thetemperature data for a specified power level as a function of time, orany other variables found to affect tissue properties. The expectedtemperature response may thus be used as a parameter in a power supplysafety algorithm. For example, if the measured temperature response isnot within a predefined range of the expected temperature response, thepower supply will automatically shut down.

[0081] Other control algorithms may also be employed. For example, analgorithm may be employed to shut down energy delivery if the sensedtemperature does not rise by a certain number of degrees in apre-specified amount of time after energy delivery begins. Preferably,if the sensed temperature does not increase more than about 10° C. inabout 3 seconds, the power supply is shut off. More preferably, if thesensed temperature does not increase more than about 10° C. in about 1second, the power supply is shut off.

[0082] Another way to stop energy delivery includes shutting down apower supply if the temperature ramp is not within a predefined range atany time during energy delivery. For, example, if the measured rate oftemperature change does not reach a predefined value, the power supplywill stop delivery of the RF energy. The predefined values arepredetermined and based on empirical data. Generally, the predefinedvalues are based on the duration of time RF energy is delivered and thepower-level applied. A suitable predefined rate of temperature change tostop energy delivery is from 8° C./second to 15° C./second in the first5 seconds (preferably in the first 2 seconds) of commencing energydelivery.

[0083] Other algorithms include shutting down a power supply if amaximum temperature setting is exceeded or shutting down a power supplyif the sensed temperature suddenly changes, such a change includeseither a drop or rise, this change may indicate failure of thetemperature sensing element. For example, the generator or power supplymay be programmed to shut off if the sensed temperature drops more thanabout 10° C. in about 0.1 to 1 seconds and more preferably in about 0.2seconds.

[0084] In another configuration, the power is terminated when themeasured temperature exceeds a pre-selected temperature or exceeds theset point temperature by a pre-selected amount. For example, when theset point is exceeded by 5 to 20° C., more preferably 15° C. the powerwill terminate.

[0085] In another configuration, power is terminated when the measuredtemperature (averaged over a time window) exceeds a pre-selectedtemperature. For example, power may be terminated when the measuredtemperature (averaged over 1 to 5 seconds and preferably averaged over 2seconds) exceeds the preset temperature by a predetermined amount. Thepredetermined amount is generally from 1 to 10° C. and preferably about5° C. Suitable preset temperatures are from 60 to 80° C. and mostpreferably about 65° C. Accordingly, in one exemplary configuration, thepower is stopped when the measured temperature (averaged over 2 seconds)exceeds 70° C.

[0086] In another configuration, the power is terminated when the amountof energy delivered exceeds a maximum amount. A suitable maximum amountis 120 Joules for an energy delivery apparatus delivering energy to theairways of lungs.

[0087] In another configuration, the power is shut down depending on animpedance measurement. The impedance is monitored across a treated areaof tissue within the lung. Impedance may also be monitored at more thanone site within the lungs. The measuring of impedance may be but is notnecessarily performed by the same electrodes used to deliver the energytreatment to the tissue. The impedance may be measured as is known inthe art and as taught in U.S. application Ser. No. 09/436,455 which isincorporated by reference in its entirety. Accordingly, in one variationof the present invention, the power is adjusted or shut off when ameasured impedance drops below a preset impedance value. When using theenergy delivering device of the present invention to treat airways, asuitable range for the preset impedance value is from 40 to 60 ohms andpreferably about 50 ohms.

[0088] In another variation, the energy delivery apparatus is configuredto deliver an amount of power up to a maximum power. The maximum powercan be from 10 to 40 watts and preferably from 15 to 20 watts.

[0089] In yet another configuration, the power supply is configured toshut down if the power delivered exceeds a maximum power and themeasured temperature drops by a critical temperature difference within asampling period of time. A suitable maximum power is from 15 to 20 Wattsand preferably about 17 watts. The sampling period of time generallyranges from 0.1 to 1.0 seconds and preferably is about 0.5 seconds. Asuitable range for the critical temperature difference is about 2° C.

[0090] It is to be understood that any of the above algorithms andshut-down configurations may be combined in a single controller.However, algorithms having mutually exclusive functions may not becombined.

[0091] While the power supply or generator preferably includes oremploys a microprocessor, the invention is not so limited. Other meansknown in the art may be employed. For example, the generator may behardwired to run one or more of the above discussed algorithms.

[0092] The controller is preferably programmable and configured toreceive and manipulate other signals than the examples provided above.For example, other useful sensors may provide input signals to theprocessor to be used in determining the power output for the next step.The treatment of an airway may also involve placing a visualizationsystem such as an endoscope or bronchoscope into the airways. Thetreatment device is then inserted through or next to the bronchoscope orendoscope while visualizing the airways. Alternatively, thevisualization system may be built directly into the treatment deviceusing fiber optic imaging and lenses or a CCD and lens arranged at thedistal portion of the treatment device. The treatment device may also bepositioned using radiographic visualization such as fluoroscopy or otherexternal visualization means.

EXAMPLES

[0093] A system to treat airways in accordance with the presentinvention was built and tested in vivo on two canines. The systemincluded an energy delivering apparatus having a distal basket. Thebasket included electrode legs and a temperature sensor mounted to oneof the legs. The system also included a generator programmed to measurethe temperature change per energy unit during the first half-second oftreatment. A PID gain factor was adjusted depending on the measuredtissue response. That is, the gain factor was adjusted based on thetemperature change per joule output during the first half second. Ingeneral, this corresponds to a higher gain for less responsive tissueand lower gain for more responsive tissue.

[0094] After treating the test subjects with a general anesthetic, RFenergy was delivered to target regions using an energy delivery deviceand generator as described above. In particular, energy activations wereperformed on all available intraparenchymal airways three millimeters orlarger in diameter in both lungs. Three hundred sixty-three activationsusing a 65° C. temperature setting were performed in the two animals(i.e., 180 activations per animal). Additionally, in twenty of theactivations in each animal, the energy delivery device was deliberatelydeployed improperly to provide a “Stress” condition.

[0095] In each activation, the measured temperature reached andstabilized at 65° C. or, in the case of the twenty activations under“stress” conditions, the power properly shut off. Thus, the presentinvention can successfully treat lung tissue with a variable gainsetting and various safety algorithms to safely maintain a presettemperature at the electrode or lung tissue surface. This temperaturecontrol is particularly advantageous when treating the airways of lungsto reduce asthma symptoms.

[0096] This invention has been described and specific embodiments orexamples of the invention have been portrayed to convey a properunderstanding of the invention. The use of such examples is not intendedto limit the invention in any way. Additionally, to the extent thatthere are variations of the invention which are within the spirit of thedisclosure and are equivalent to features found in the claims, it is theintent that the claims cover those variations as well. All equivalentsare considered to be within the scope of the claimed invention, eventhose which may not have been set forth herein merely for the sake ofbrevity. Also, the various aspects of the invention described herein maybe modified and/or used in combination with such other aspects alsodescribed to be part of the invention either explicitly or inherently toform other advantageous variations considered to be part of theinvention covered by the claims which follow.

[0097] The invention described herein expressly incorporates thefollowing co-pending applications by reference in their entirety: U.S.application Ser. No. 09/095,323; U.S. application Ser. No. 09/095,323;U.S. application Ser. No. 09/349,715; U.S. application Ser. No.09/296,040; U.S. application Ser. No. 09/436,455; and U.S. applicationSer. No. 09/535,856.

1. A system for delivering energy to an airway wall of a lungcomprising: an energy delivering apparatus comprising a flexibleelongated member and a distal expandable basket, said expandable baskethaving at least one electrode for transferring energy to said airwaywall and at least one temperature sensor for measuring temperature(T_(M)) of said airway wall when energy is delivered to said airwaywall; and a PID controller for determining a new power set point(P_(i+1)) based on an error (e) between a preset temperature (T_(S)) andsaid measured temperature (T_(M)) wherein said PID controller applies analgorithm having a variable gain factor (G).
 2. The system of claim 1wherein said algorithm is P_(i+1)=P_(i)+G(αe_(i)+βe_(i−1)+γe_(i−2))where α, β and γ are preset values.
 3. The system of claim 2 whereinsaid controller is configured such that G is reset 0.1 to 2 secondsafter energy delivery has begun.
 4. The system of claim 3 wherein saidcontroller is configured such that G is reset 0.5 seconds after energydelivery has begun.
 5. The system of claim 4 wherein said controller isconfigured such that G is reset to 0.9 to 1.0 if a temperature rise in °C. per Joule is less than or equal to 2.5.
 6. The system of claim 4wherein said controller is configured such that G is reset to 0.4 to 0.5if a temperature rise in ° C. per Joule is between 2.5 to 5.0.
 7. Thesystem of claim 4 wherein said controller is configured such that G isreset to 0.2 to 0.3 if a temperature rise in ° C. per Joule is equal to5.0 to 7.5.
 8. The system of claim 4 wherein said controller isconfigured such that G is reset to 0.1 to 0.2 if a temperature rise in °C. per Joule is greater than 7.5.
 9. The system of claim 2 wherein α isfrom 1 to 2,
 10. The system of claim 9 wherein β is from −1 to −2. 11.The system of claim 10 wherein γ is from −0.5 to 0.5
 12. The system ofclaim 11 wherein α, β, γ are 1.6, −1.6, and 0.0 respectively.
 13. Thesystem of claim 1 wherein said controller is configured such that saidenergy delivery is terminated if said energy delivered exceeds a maximumenergy.
 14. The system of claim 13 wherein said maximum energy is 120joules.
 15. The system of claim 1 wherein said controller is configuredto deliver energy for an activation time period.
 16. The system of claim15 wherein said controller is configured such that the activation timeperiod is up to 15 seconds.
 17. The system of claim 16 wherein saidcontroller is configured such that the activation time period is 8 to 12seconds.
 18. The system of claim 17 wherein said controller isconfigured such that the activation time period is 10 seconds.
 19. Thesystem of claim 1 wherein said controller is configured such that T_(S)is set at a value between 60 to 80° C.
 20. The system of claim 19wherein T_(S) is set at 65° C.
 21. The system of claim 1 wherein saidcontroller is configured to measure impedance and said energy deliveryis terminated when said impedance drops below a preset impedance value.22. The system of claim 21 wherein said preset impedance value is 40 to60 ohms.
 23. The system of claim 1 wherein said controller is configuredto terminate said energy delivery if said T_(M) exceeds T_(S) by apre-selected value.
 24. The system of claim 23 wherein said pre-selectedvalue is 10° C.
 25. The system of claim 23 wherein said pre-selectedvalue is 15° C.
 26. The system of claim 23 wherein said pre-selectedvalue is 20° C.
 27. The system of claim 1 wherein said controller isconfigured to terminate said energy delivery if said output power isgreater or equal to a nominal output power and said T_(M) drops by acritical temperature difference within a sampling period.
 28. The systemof claim 27 wherein said nominal output power is set at a value of atleast 17 watts.
 29. The system of claim 28 wherein said sampling periodis set at a value of at least 0.5 seconds.
 30. The system of claim 29wherein said critical temperature difference is 2° C.
 31. The system ofclaim 1 wherein said controller is configured to terminate said energydelivery if said T_(M) averaged over a time window exceeds T_(S) by afixed temperature difference.
 32. The system of claim 31 wherein saidfixed temperature difference is between 1 and 10° C.
 33. The system ofclaim 32 wherein said fixed temperature difference is 5° C.
 34. Thesystem of claim 33 wherein said time window is between 1 and 5 seconds.35. The system of claim 34 wherein said time window is 2 seconds. 36.The system of claim 1 wherein said controller is configured to terminateif said measured temperature drops by 10 or more ° C. in a sampleperiod.
 37. The system of claim 36 wherein the sample period is 1.0seconds.
 38. The system of claim 36 wherein the sample period is 0.2seconds.
 39. The system of claim 1 wherein the gain factor is initiallyequal to a value between 0.4 and 0.5.
 40. A method for treating a lungby transferring energy from an active region of an energy deliveryapparatus to an airway wall of said lung, said energy delivery apparatushaving a flexible elongate body and a distal section and said activeregion being located in said distal section, said energy deliveryapparatus further having a temperature sensor located in said distalsection for measuring a temperature (T_(M)) of said airway wall, saidmethod comprising: setting a preset temperature (T_(S)); determining apower set point (P_(i)) to deliver energy from said active region tosaid target medium; measuring said T_(M) using said temperature sensor;determining a new power set point (P_(i+1)) based on an error (e)between said preset temperature (T_(S)) and said measured temperature(T_(M)) using a PID algorithm.
 41. A process for transferring energy toa target medium using an energy delivery apparatus, said energy deliveryapparatus having a flexible elongate body and a distal section whereinsaid distal section includes an expandable basket with at least oneactive region for transferring energy to said target medium, said energydelivery apparatus further having a temperature sensor located in saiddistal section for measuring a temperature (T_(M)) of said targetmedium, said process comprising: setting a preset temperature (T_(S));determining a power set point (P_(i)) to deliver energy from said activeregion to said target medium; measuring said T_(M) using saidtemperature sensor; determining a new power set point (P_(i+1)) based onan error (e) between said preset temperature (T_(S)) and said measuredtemperature (T_(M)) using an algorithm having a variable gain factor.42. The process of claim 41 wherein said algorithm is:P_(i+1)=P_(i)+G(αe_(i)+βe⁻¹+γe_(i−2)) where α, β and γ are presetvalues.
 43. The process of claim 42 comprising resetting G 0.1 to 2seconds after energy delivery has begun.
 44. The process of claim 43comprising resetting G 0.5 seconds after energy delivery has begun. 45.The process of claim 44 comprising resetting G to 0.9 to 1.0 if atemperature rise in ° C. per Joule is less than or equal to 2.5.
 46. Theprocess of claim 44 comprising resetting G to 0.4 to 0.5 if atemperature rise in ° C. per Joule is between 2.5 to 5.0.
 47. Theprocess of claim 44 comprising resetting G to 0.2 to 0.3 if atemperature rise in ° C. per Joule is equal to 5.0 to 7.5.
 48. Theprocess of claim 44 comprising resetting G to 0.1 to 0.2 if atemperature rise in ° C. per Joule is greater than 7.5.
 49. The processof claim 42 comprising setting α between 1 and
 2. 50. The process ofclaim 49 comprising setting β between −1 to −2.
 51. The process of claim50 comprising setting γ to −0.5 to 0.5.
 52. The process of claim 51comprising setting α, β, γ to 1.6, −1.6, and 0.0 respectively.
 53. Theprocess of claim 41 comprising terminating said energy delivery if saidenergy delivered exceeds a maximum energy.
 54. The process of claim 53wherein said maximum energy is 120 joules.
 55. The process of claim 41wherein energy is delivered for an activation period.
 56. The process ofclaim 55 wherein said activation period up to 15 seconds.
 57. Theprocess of claim 56 wherein said activation period is 8 to 12 seconds.58. The process of claim 57 wherein said activation period is 10seconds.
 59. The process of claim 41 comprising setting T_(S) at a valuebetween 60 to 80° C.
 60. The process of claim 59 comprising settingT_(S) at 65° C.
 61. The process of claim 41 further comprising measuringimpedance and terminating said energy delivery when said impedance dropsbelow a preset impedance value.
 62. The process of claim 61 wherein saidpreset impedance value is from 40 to 60 ohms.
 63. The process of claim41 comprising terminating said energy delivery if said T_(M) exceedsT_(S) by a pre-selected value.
 64. The process of claim 63 wherein saidpre-selected value is 10° C.
 65. The process of claim 63 wherein saidpre-selected value is 15° C.
 66. The process of claim 63 wherein saidpre-selected value is 20° C.
 67. The process of claim 41 comprisingterminating said energy delivery if an output power is greater or equalto a nominal output power and said T_(M) drops by a critical temperaturedifference within a sampling period.
 68. The process of claim 67 whereinsaid nominal output power is set at a value of at least 17 watts. 69.The process of claim 68 wherein said sampling period is set at a valueof at least 0.5 seconds.
 70. The process of claim 69 wherein saidcritical temperature difference is 2° C.
 71. The process of claim 41comprising terminating said energy delivery if said T_(M) averaged overa time window exceeds T_(S) by a fixed temperature difference.
 72. Theprocess of claim 71 wherein said fixed temperature difference is a valuebetween 1 and 10° C.
 73. The process of claim 72 wherein said fixedtemperature difference is 5° C.
 74. The process of claim 73 wherein saidtime window is between 1 and 5 seconds.
 75. The process of claim 74wherein said time window is 2 seconds.
 76. The process of claim 41wherein said delivering energy to a target medium is performed bydelivering energy to an airway wall of a lung in vivo.
 77. The processof claim 41 wherein said delivering energy to a target medium isperformed by delivering energy to an airway wall of an excised lung. 78.The process of claim 41 wherein said delivering energy to a targetmedium is performed by delivering energy to a sponge or towel.
 79. Thesystem of claim 1 wherein said PID controller applies an algorithmhaving a plurality of variable gain factors.
 80. The system of claim 79wherein said algorithm is P_(i+1)=P_(i+)(G₁e_(i)+G₂e_(i−1)+G₃e_(i−2))where G₁, G₂ and G₃ are variable gain factors.
 81. The system of claim80 wherein said controller is configured such that said variable gainfactors are reset 0.1 to 2 seconds after energy delivery has begun. 82.The system of claim 81 wherein said controller is configured such thatsaid variable gain factors are reset 0.5 seconds after energy deliveryhas begun.
 83. The system of claim 82 wherein said controller isconfigured such that G₁, G₂ and G₃ are reset to 0.90 to 2.00, −0.90 to−2.00 and 0.5 to −0.5 respectively if a temperature rise in ° C. perJoule is less than or equal to 2.5.
 84. The system of claim 82 whereinsaid controller is configured such that G₁, G₂ and G₃ are reset to 0.40to 1.00, 0.40 to −1.00 and 0.25 to −0.25 respectively if a temperaturerise in ° C. per Joule is between 2.5 to 5.0.
 85. The system of claim 82wherein said controller is configured such that G₁, G₂ and G₃ are resetto 0.20 to 0.60, −0.20 to −0.60 and 0.15 to −0.15 respectively if atemperature rise in ° C. per Joule is equal to 5.0 to 7.5.
 86. Thesystem of claim 82 wherein said controller is configured such that G₁,G₂ and G₃ are reset to 0.10 to 0.40, −0.10 to −0.40 and 0.10 to −0.10respectively if a temperature rise in ° C. per Joule is greater than7.5.
 87. The system of claim 80 wherein each of said variable gainfactors is equal to a product of at least one preset value and at leastone variable value.
 88. The process of claim 41 wherein said PIDcontroller applies an algorithm having a plurality of variable gainfactors.
 89. The process of claim 88 wherein said algorithm isP_(i+1)=P_(i)+(G₁e_(i)+G₂e_(i−1)+G₃e_(i−2)) where G₁, G₂ and G₃ arevariable gain factors.
 90. The process of claim 89 wherein saidcontroller is configured such that said variable gain factors are reset0.1 to 2 seconds after energy delivery has begun.
 91. The process ofclaim 90 wherein said controller is configured such that said variablegain factors are reset 0.5 seconds after energy delivery has begun. 92.The process of claim 91 wherein said controller is configured such thatG₁, G₂ and G₃ are reset to 0.90 to 2.00, −0.90 to −2.00 and 0.50 to−0.50 respectively if a temperature rise in ° C. per Joule is less thanor equal to 2.5.
 93. The process of claim 91 wherein said controller isconfigured such that G₁, G₂ and G₃ are reset to 0.40 to 1.00, −0.40 to−1.00 and 0.25 to −0.25 respectively if a temperature rise in ° C. perJoule is between 2.5 to 5.0.
 94. The process of claim 91 wherein saidcontroller is configured such that G₁, G₂ and G₃ are reset to 0.20 to0.60, −0.20 to −0.60 and 0.15 to −0.15 respectively if a temperaturerise in ° C. per Joule is equal to 5.0 to 7.5.
 95. The process of claim91 wherein said controller is configured such that G₁, G₂ and G₃ arereset to 0.10 to 0.40, −0.10 to −0.40 and 0.10 to −0.10 respectively ifa temperature rise in ° C. per Joule is greater than 7.5.
 96. Theprocess of claim 91 wherein each of said variable gain factors is equalto a product of at least one preset value and at least one variablevalue.
 97. The system of claim 1 wherein the energy delivery apparatusis configured to deliver an amount of power up to a maximum power. 98.The system of claim 97 wherein the maximum power is 10 to 40 watts. 99.The system of claim 98 wherein the maximum power is 15 to 20 watts. 100.The process of claim 41 wherein the energy delivery apparatus isconfigured to deliver an amount of power up to a maximum power.
 101. Theprocess of claim 100 wherein the maximum power is 10 to 40 watts. 102.The process of claim 101 wherein the maximum power is 15 to 20 watts.